The kinetics of extraction of the medicinal ginger bioactive compounds using hot compressed water

•Selective extraction of ginger bioactive compound can be achieved at the different operating condition.•The dielectric constant does not significantly contribute to the extraction efficiency.•The dehydration and degradation of 6-gingerol to 6-shogaol and other compound occur from the temperature of 140 °C.

Zingiber officinale or ginger known for its high medicinal compounds is extracted using hot compressed water (HCW). The two most important bioactive compounds namely 6-gingerol and 6-shogaol in the ginger extracts are analyzed using HPLC. The effects of temperature and time of extraction on 6-gingerol and 6-shogaol are studied using HCW extraction. It is found that HCW extraction can extract these two bioactive compounds; 6-gingerol at 130 °C and 30 min whilst 6-shogaol at 170 °C and 20 min. This finding shows that HCW extraction is potentially used in selective extraction of bioactive compounds at different conditions of HCW. The kinetics of extraction for both bioactive compounds is studied from the optimum temperatures obtained. The overall mass transfer coefficient which represents the extraction efficiency is calculated using mass transfer model. The optimum values of the overall mass transfer coefficient (k) for 6-gingerol is 8 × 10−7 m/s at 130 °C whilst for 6-shogaol, is 18 × 10−7 m/s at 170 °C using HCW extraction. The relationship between the overall mass transfer coefficient and the dielectric constant of various solvents for 6-gingerol is identified. Similar relationship is identified for 6-shogaol using HCW as solvent. The dielectric constant does not contribute to the extraction efficiency of 6-gingerol and 6-shogaol.